Financial constraints will force CCGs to become "far far bigger" than PCTs, the chair of the BMA's GPC has claimed.
Dr Laurence Buckman told MiP the CCG sizes that are currently seen on the ground will not be "economically viable" once the GP-led groups formally take hold of commissioning budgets.
CCG size varies considerably across England – with the smallest being the Red House group in Hertfordshire, which serves a population of 18,000 and the recently-merged Cambridgeshire and Peterborough CCG covering a population of 850,000 being the largest in the country.
Dr Buckman predicted the £25 management cost allowance would serve to destroy this variation and introduce a "uniform CCG size".
"Our concern is when everyone else has raided the already tiny budgets CCGs will be working with, there will so little money left they will have no other option than to merge into even bigger units to survive," he said.
"If CCGs are to be economically viable with running costs of £25 per head, they will all have to become enormous – far far bigger than PCT size.
"The current variation in CCG size will not be allowed to continue."
However, Dr Donal Hynes, Vice-Chair of the NHS Alliance, doesn't share Dr Buckman's concerns around CCG size as he claimed large commissioning support organisations with economies of scale will be "cost-effective enough" to allow CCGs to remain "the size they set out to be".
Dr Buckman also told MiP the "unrealistic timetable" for authorisation is also causing some CCGs to rush key decisions
Such decisions include: procuring services from the private sector, organising legal entities and interviewing for job roles before job specifications have been finalised.
"The timescale of this handover period is completely mismanaged and as such, the majority of CCGs will not be ready to be authorised when their time comes," he said.
By Louise Naughton